A number of different types of sewer cleaners are known to the art. Manual systems are still used in numerous localities and employ buckets dragged through the sewer lines to remove debris.
In recent years, combination sewer and catch basin cleaners have been developed to speed cleaning and to reduce cleaning costs. Many of the machines employ the general concepts of Dougene's U.S. Pat. No. 287,811 issued on Nov. 6, 1883 and entitled "Cleaning Sewers". This patent describes a combination water injection and water pumping machine for flushing a sewer with water and removing the water and collected debris from settling chambers associated with the sewer lines.
More recent developments are described in Parmallee's U.S. Pat. No. 3,600,225 issued Aug. 17, 1971 for "Pipe Cleaning" and Shaddock's U.S. Pat. No. 3,658,589 issued Apr. 25, 1972 for "Catch Basin and Sewer Pipe Cleaner". In both of these patents, water under pressure is injected into sewer laterals through specially designed nozzles to wash debris into a manhole or catch basin.
The nozzles employed in the latter two patents have a plurality of water jets oriented toward the manhole or catch basin after the nozzle is inserted in the lateral. When the water is forced through the jets, the nozzles are driven further into the laterals. When the nozzles are retracted, the jets clean the sewer by a knife-like action and the additional water flushes loosened debris toward the catch basin or manhole.
Parmalee and Shaddock differ primarily in the water injection and water recovery systems. In Parmalee, a screen is placed over a water recovery hose and water is pumped from a manhole into a settling tank, through a grit remover and centrigugal separator to a storage tank for being reused in the cleaning process. Parmalee does not include a vacuum system for removing large solids from the manhole. Shaddock, on the other hand, employs a vacuum system for pneumatically conveying debris and water from the catch basin into a material collection chamber.
While the systems described in these two patents are much more efficient and economical than manual cleaning systems, Parmalee does not employee vacuum loading and Shaddock does not have the capability of water regeneration. Shaddock's machine must be reloaded with water at the beginning of each cleaning operation, or sewer cleaning must be accomplished at a location near a water supply, such as a fire hydrant or water main. This deficiency results in extended downtime, inconvenience and loss of overall efficiency.
An improved sewer and catch basin cleaner is described in U.S. Pat. No. 4,134,174 issued on Jan. 16, 1979 to Flynn and Wurster. The unit described in this patent includes a water tank and a pump and hose connected thereto for supplying water under pressure to the sewer laterals. The unit also includes a body, a vacuum hose and a vacuum pump downstream of the hose and body for vacuum loading water and debris from a manhole or catch basin into the body. The improvements disclosed in this patent include a conduit between the body and water tank, a pump connected to the conduit and filter means located in the body for screening impurities before the water reaches the conduit.
In the preferred embodiment of the Flynn and Wurster patent, two screens are used in the body and a system is provided for cleaning one of the screens by causing air to periodically pass through the screen in a direction which is reverse to that of the water flow. It is also disclosed that a water strainer and centrifugal separator may be employed to provide further purification of the water after it enters the conduit but before it reaches the water tank.
Another improvement disclosed in the Flynn and Wurster patent includes an overfill protection system for the body which includes sensors and a vent for the body when water reaches a preselected height. The vent reduces the negative pressure in the body and prevents further vacuum loading.
Yet another improvement disclosed in the Flynn and Wurster patent is the use of an ejector plate in combination sewer and catch basin cleaners. In addition to providing a convenient way of emptying the body, the disclosed ejector plate acts as yet another filter to separate large particles and prevent them from reaching the two screens. The ejector is moved by a hydraulic ram.
Finally, the Flynn and Wurster patent discloses an elongate boom mounted behind the truck cab but extending thereover, the boom being horizontally rotatable and vertically elevatable and supporting both the water and vacuum hoses. The boom and hose arrangement permits optimum maneuverability of the hoses while minimizing obstruction of streets or highways during cleaning.
While the sewer and catch basin cleaner disclosed in the Flynn and Wurster patent represents a significant advancement in the art, it has been found that water removed during the vacuum operation may exceed the amount of water introduced through the cleaning nozzles. The excess water comes from normal sewer flow and may amount to a trickle or a substantial flow depending on the type of sewer system, the time of day, the amount of recent rainfall, etc. The excess water creates a problem because the loading capacity usually exceeds the capacity of the water filtration system. A manually operated drain was employed in the Flynn and Wurster device but was not satisfactory because the drain could become plugged and the truck would have to be repositioned to dump the water.
Another problem encountered with this type of prior art sewer and catch basin cleaner was the tailgate operation and sealing. Hydraulic cylinders were required to open and close the tailgate adding to the expense of the unit and creating additional sources of repair problems. Moreover, the tailgate gasket for a combination sewer and catch basin cleaner required frequent repair. The seal must prevent leakage and insure sufficient vacuum in the water collection body. Moreover, manufacturing tolerances had to be very close to insure a proper seal.
Inflatable seals are known for several different types of systems known to the present inventor. They are employed in railroad systems to insure a proper seal between freight cars and freight car loading devices. They are also employed on one type of industrial vacuum loader in which a material collection chamber and filter are raised by a hydraulic ram to dump a material collection body. In this device, an inflatable seal is used at the junction of the filter and the vacuum pump assembly.
The present inventor is also aware of a prior art sewer and catch basin cleaner which has a means for pumping water from the collection body when it is filled. In this machine, the pump which is used to create a vacuum inside the collector body is also employed to pump water out of the body and into a hose which may be placed back into the sewer. The water which is removed from the body is dirty water and body emptying cannot be done at the same time that sewer cleaning continues. This system then does not overcome downtime problems in the overall sewer cleaning operation.